Pathological hoarding is a mental disorder that leads to clutter in the home and poses a significant burden for those affected and their families. Individuals struggle with an irresistible urge to accumulate large amounts of possessions and feel unable to part with them, even when they hold no monetary value or practical use. Unlike compulsive rituals, pathological hoarding is often associated with positive emotions. The disorder frequently runs a chronic course and is difficult to treat. This book provides information on the current state of research regarding the description, classification, epidemiology, differential diagnosis, and progression of pathological hoarding. After presenting various diagnostic methods, it introduces cognitive-behavioral therapeutic options that have been developed in recent years.